Method for measuring solid-liquid interfacial electric field

Abstract

An interfacial electric field intensity of a surface is measured by covalently binding a monolayer of a voltage sensitive chromophore to the surface and irradiating it with actinic radiation while it is in contact with a liquid and measuring a first fluorescence emission spectrum. A solution of the voltage sensitive chromophore dissolved in a sample of the liquid is also irradiated with actinic radiation and a second fluorescence emission spectrum is measured. The first and second fluorescence emission spectra are compared to determine the interfacial electric field intensity.

The invention claimed is: 
     
       1. A method for measuring an interfacial electric field intensity, comprising:
 providing a surface having a reactive carbocyclic aromatic linking group covalently attached thereon; 
 providing a voltage sensitive chromophore precursor including a p-substituted dialkylamino aryl group that is conjugatively linked to a terminal N-containing heterocyclic aromatic group; 
 reacting the voltage sensitive chromophore precursor with the reactive carbocyclic aromatic linking group that is covalently attached to the surface to form a monolayer of a voltage sensitive chromophore that is covalently bound to the surface; 
 irradiating the monolayer of the covalently bound voltage sensitive chromophore with actinic radiation while it is in contact with a liquid and measuring a first fluorescence emission spectrum; 
 providing a voltage sensitive chromophore solution of the voltage sensitive chromophore dissolved in a sample of the liquid; 
 irradiating the voltage sensitive chromophore solution with actinic radiation and measuring a second fluorescence emission spectrum; and 
 comparing the first and second fluorescence emission spectra to determine an interfacial electric field intensity, wherein comparing the first and second fluorescence emission spectra includes performing a mathematical analysis to determine at least one parameter characterizing a difference between the first and second fluorescence emission spectra, and wherein the interfacial electric field intensity is determined responsive to the determined at least one parameter. 
 
     
     
       2. The method of  claim 1 , wherein the reactive carbocyclic aromatic linking group includes a benzyl halide group. 
     
     
       3. The method of  claim 1 , wherein the N-containing heterocyclic aromatic group is a pyridinyl group. 
     
     
       4. The method of  claim 1 , wherein the voltage sensitive chromophore is a reaction product where the reactive carbocyclic aromatic linking group is bonded to the terminal N-containing heterocyclic aromatic group of the voltage sensitive chromophore precursor. 
     
     
       5. The method of  claim 1 , wherein the liquid is acetone, methanol, water or chloroform. 
     
     
       6. The method of  claim 1 , wherein comparing the first and second fluorescence emission spectra includes:
 determining a first spectral peak for the first fluorescence emission spectrum; 
 determining a second spectral peak for the second fluorescence emission spectrum; and 
 determining a difference parameter representing a wavelength difference or a wave number difference between the first and second spectral peaks; wherein the interfacial electric field intensity is determined responsive to the difference parameter. 
 
     
     
       7. The method of  claim 1 , wherein comparing the first and second fluorescence emission spectra includes:
 specifying first and second wavelengths; 
 determining a first intensity ratio parameter representing a first intensity ratio between a value of the first fluorescence emission spectrum at the first wavelength and a value of the first fluorescence emission spectrum at the second wavelength; 
 determining a second intensity ratio parameter representing a second intensity ratio between a value of the second fluorescence emission spectrum at the first wavelength and a value of the second fluorescence emission spectrum at the second wavelength; and 
 wherein the interfacial electric field intensity is determined responsive to the first and second intensity ratio parameters. 
 
     
     
       8. The method of  claim 1 , wherein the surface having the reactive carbocyclic aromatic linking group covalently attached thereon is formed by:
 providing a solution including the reactive carbocyclic aromatic linking group; 
 providing a surface capable of reacting with the reactive aromatic linking group; and 
 bringing the solution into contact with the surface, thereby reacting the reactive carbocyclic aromatic linking group with the surface to attach the reactive carbocyclic aromatic linking group to the surface with a covalent linkage. 
 
     
     
       9. The method of  claim 1 , wherein the surface is a silica surface or a polymer surface. 
     
     
       10. The method of  claim 1 , wherein the surface is non-biological.